Pino Toscano
2020-Sep-23 15:57 UTC
[Libguestfs] [common PATCH 0/3] SELinux_relabel: relabel only if enforcing (RHBZ#1828952)
Continuation/rework of: https://www.redhat.com/archives/libguestfs/2020-May/msg00020.html This is my approach, as I explained here: https://bugzilla.redhat.com/show_bug.cgi?id=1828952#c4 https://www.redhat.com/archives/libguestfs/2020-May/msg00035.html IOW: do not attempt to relabel if the guest is not enforcing, as it is either useless or may fail; few words more are in the comments of patch #3. Pino Toscano (2): mlcustomize: refactor reading from /etc/selinux/config mlcustomize: do not relabel if not enforcing (RHBZ#1828952) Richard W.M. Jones (1): mlcustomize: Refactor SELinux_relabel code. mlcustomize/SELinux_relabel.ml | 153 ++++++++++++++++++++------------- 1 file changed, 94 insertions(+), 59 deletions(-) -- 2.26.2
Pino Toscano
2020-Sep-23 15:57 UTC
[Libguestfs] [common PATCH 1/3] mlcustomize: Refactor SELinux_relabel code.
From: "Richard W.M. Jones" <rjones@redhat.com> This shouldn't change the effect of this code. --- mlcustomize/SELinux_relabel.ml | 121 ++++++++++++++++++--------------- 1 file changed, 65 insertions(+), 56 deletions(-) diff --git a/mlcustomize/SELinux_relabel.ml b/mlcustomize/SELinux_relabel.ml index 44995df..5df1f08 100644 --- a/mlcustomize/SELinux_relabel.ml +++ b/mlcustomize/SELinux_relabel.ml @@ -28,65 +28,74 @@ module G = Guestfs let array_find a l List.mem a (Array.to_list l) -let relabel (g : G.guestfs) - (* Is the guest using SELinux? *) - if g#is_file ~followsymlinks:true "/usr/sbin/load_policy" && - g#is_file ~followsymlinks:true "/etc/selinux/config" then ( - (* Is setfiles / SELinux relabelling functionality available? *) - if g#feature_available [| "selinuxrelabel" |] then ( - (* Use Augeas to parse /etc/selinux/config. *) - g#aug_init "/" (16+32) (* AUG_SAVE_NOOP | AUG_NO_LOAD *); - (* See: https://bugzilla.redhat.com/show_bug.cgi?id=975412#c0 *) - ignore (g#aug_rm "/augeas/load/*[\"/etc/selinux/config/\" !~ regexp('^') + glob(incl) + regexp('/.*')]"); - g#aug_load (); - debug_augeas_errors g; - - (* Get the SELinux policy name, eg. "targeted", "minimum". - * Use "targeted" if not specified, just like libselinux does. +let rec relabel (g : G.guestfs) + (* Is the guest using SELinux? (Otherwise this is a no-op). *) + if is_selinux_guest g then ( + try + use_setfiles g; + (* That worked, so we don't need to autorelabel. *) + g#rm_f "/.autorelabel" + with Failure _ -> + (* This is the fallback in case something in the setfiles + * method didn't work. That includes the case where a non-SELinux + * host is processing an SELinux guest, and other things. *) - let policy - let config_path = "/files/etc/selinux/config" in - let selinuxtype_path = config_path ^ "/SELINUXTYPE" in - let keys = g#aug_ls config_path in - if array_find selinuxtype_path keys then - g#aug_get selinuxtype_path - else - "targeted" in + g#touch "/.autorelabel" + ) - g#aug_close (); +and is_selinux_guest g + g#is_file ~followsymlinks:true "/usr/sbin/load_policy" && + g#is_file ~followsymlinks:true "/etc/selinux/config" - (* Get the spec file name. *) - let specfile - sprintf "/etc/selinux/%s/contexts/files/file_contexts" policy in +and use_setfiles g + (* Is setfiles / SELinux relabelling functionality available? *) + if not (g#feature_available [| "selinuxrelabel" |]) then + failwith "no selinux relabel feature"; - (* RHEL 6.2 - 6.5 had a malformed specfile that contained the - * invalid regular expression "/var/run/spice-vdagentd.\pid" - * (instead of "\.p"). This stops setfiles from working on - * the guest. - * - * Because an SELinux relabel writes all over the filesystem, - * it seems reasonable to fix this problem in the specfile - * at the same time. (RHBZ#1374232) - *) - if g#grep ~fixed:true "vdagentd.\\pid" specfile <> [||] then ( - debug "fixing invalid regular expression in %s" specfile; - let old_specfile = specfile ^ "~" in - g#mv specfile old_specfile; - let content = g#read_file old_specfile in - let content - String.replace content "vdagentd.\\pid" "vdagentd\\.pid" in - g#write specfile content; - g#copy_attributes ~all:true old_specfile specfile - ); + (* Use Augeas to parse /etc/selinux/config. *) + g#aug_init "/" (16+32) (* AUG_SAVE_NOOP | AUG_NO_LOAD *); + (* See: https://bugzilla.redhat.com/show_bug.cgi?id=975412#c0 *) + ignore (g#aug_rm "/augeas/load/*[\"/etc/selinux/config/\" !~ regexp('^') + glob(incl) + regexp('/.*')]"); + g#aug_load (); + debug_augeas_errors g; - (* Relabel everything. *) - g#selinux_relabel ~force:true specfile "/"; + (* Get the SELinux policy name, eg. "targeted", "minimum". + * Use "targeted" if not specified, just like libselinux does. + *) + let policy + let config_path = "/files/etc/selinux/config" in + let selinuxtype_path = config_path ^ "/SELINUXTYPE" in + let keys = g#aug_ls config_path in + if array_find selinuxtype_path keys then + g#aug_get selinuxtype_path + else + "targeted" in - (* If that worked, we don't need to autorelabel. *) - g#rm_f "/.autorelabel" - ) - else ( - (* SELinux guest, but not SELinux host. Fallback to this. *) - g#touch "/.autorelabel" - ) - ) + g#aug_close (); + + (* Get the spec file name. *) + let specfile + sprintf "/etc/selinux/%s/contexts/files/file_contexts" policy in + + (* RHEL 6.2 - 6.5 had a malformed specfile that contained the + * invalid regular expression "/var/run/spice-vdagentd.\pid" + * (instead of "\.p"). This stops setfiles from working on + * the guest. + * + * Because an SELinux relabel writes all over the filesystem, + * it seems reasonable to fix this problem in the specfile + * at the same time. (RHBZ#1374232) + *) + if g#grep ~fixed:true "vdagentd.\\pid" specfile <> [||] then ( + debug "fixing invalid regular expression in %s" specfile; + let old_specfile = specfile ^ "~" in + g#mv specfile old_specfile; + let content = g#read_file old_specfile in + let content + String.replace content "vdagentd.\\pid" "vdagentd\\.pid" in + g#write specfile content; + g#copy_attributes ~all:true old_specfile specfile + ); + + (* Relabel everything. *) + g#selinux_relabel ~force:true specfile "/" -- 2.26.2
Pino Toscano
2020-Sep-23 15:57 UTC
[Libguestfs] [common PATCH 2/3] mlcustomize: refactor reading from /etc/selinux/config
Move the reading of values from /etc/selinux/config to an own function, so it can be easily reused. This is a simple refactoring. --- mlcustomize/SELinux_relabel.ml | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/mlcustomize/SELinux_relabel.ml b/mlcustomize/SELinux_relabel.ml index 5df1f08..647aeda 100644 --- a/mlcustomize/SELinux_relabel.ml +++ b/mlcustomize/SELinux_relabel.ml @@ -62,14 +62,7 @@ and use_setfiles g (* Get the SELinux policy name, eg. "targeted", "minimum". * Use "targeted" if not specified, just like libselinux does. *) - let policy - let config_path = "/files/etc/selinux/config" in - let selinuxtype_path = config_path ^ "/SELINUXTYPE" in - let keys = g#aug_ls config_path in - if array_find selinuxtype_path keys then - g#aug_get selinuxtype_path - else - "targeted" in + let policy = read_selinux_config_key g "SELINUXTYPE" "targeted" in g#aug_close (); @@ -99,3 +92,12 @@ and use_setfiles g (* Relabel everything. *) g#selinux_relabel ~force:true specfile "/" + +and read_selinux_config_key g key defval + let config_path = "/files/etc/selinux/config" in + let key_path = config_path ^ "/" ^ key in + let keys = g#aug_ls config_path in + if array_find key_path keys then + g#aug_get key_path + else + defval -- 2.26.2
Pino Toscano
2020-Sep-23 15:57 UTC
[Libguestfs] [common PATCH 3/3] mlcustomize: do not relabel if not enforcing (RHBZ#1828952)
Do not attempt to relabel a guest in case its SELinux enforcing mode is not "enforcing", as it is either pointless, or it may fail because of an invalid policy configured. --- mlcustomize/SELinux_relabel.ml | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/mlcustomize/SELinux_relabel.ml b/mlcustomize/SELinux_relabel.ml index 647aeda..db00e59 100644 --- a/mlcustomize/SELinux_relabel.ml +++ b/mlcustomize/SELinux_relabel.ml @@ -24,6 +24,9 @@ open Printf module G = Guestfs +exception SELinux_not_enforcing +(* Interal exception to signal a non-enforcing SELinux. *) + (* Simple reimplementation of Array.mem, available only with OCaml >= 4.03. *) let array_find a l List.mem a (Array.to_list l) @@ -35,12 +38,18 @@ let rec relabel (g : G.guestfs) use_setfiles g; (* That worked, so we don't need to autorelabel. *) g#rm_f "/.autorelabel" - with Failure _ -> + with + | Failure _ -> (* This is the fallback in case something in the setfiles * method didn't work. That includes the case where a non-SELinux * host is processing an SELinux guest, and other things. *) g#touch "/.autorelabel" + | SELinux_not_enforcing -> + (* This means that SELinux was not configured to be in enforcing mode, + * so silently accept this. + *) + () ) and is_selinux_guest g @@ -59,6 +68,21 @@ and use_setfiles g g#aug_load (); debug_augeas_errors g; + (* Get the SELinux enforcing mode, eg "enforcing", "permissive", + * "disabled". + * Use "disabled" if not specified, just like libselinux seems to do. + *) + let typ = read_selinux_config_key g "SELINUX" "disabled" in + (* Do not attempt any relabelling if the SELinux is not "enforcing": + * - in "permissive" mode SELinux is still running, however nothing is + * enforced: this means labels can be wrong, and "it is fine" + * - when "disabled" means SELinux is not running, so any relabelling + * is pointless (other than potentially fail due to an invalid + * SELINUXTYPE configuration) + *) + if typ <> "enforcing" then + raise SELinux_not_enforcing; + (* Get the SELinux policy name, eg. "targeted", "minimum". * Use "targeted" if not specified, just like libselinux does. *) -- 2.26.2
Richard W.M. Jones
2020-Sep-24 10:15 UTC
Re: [Libguestfs] [common PATCH 3/3] mlcustomize: do not relabel if not enforcing (RHBZ#1828952)
On Wed, Sep 23, 2020 at 05:57:50PM +0200, Pino Toscano wrote:> Do not attempt to relabel a guest in case its SELinux enforcing mode is > not "enforcing", as it is either pointless, or it may fail because of an > invalid policy configured. > --- > mlcustomize/SELinux_relabel.ml | 26 +++++++++++++++++++++++++- > 1 file changed, 25 insertions(+), 1 deletion(-) > > diff --git a/mlcustomize/SELinux_relabel.ml b/mlcustomize/SELinux_relabel.ml > index 647aeda..db00e59 100644 > --- a/mlcustomize/SELinux_relabel.ml > +++ b/mlcustomize/SELinux_relabel.ml > @@ -24,6 +24,9 @@ open Printf > > module G = Guestfs > > +exception SELinux_not_enforcing > +(* Interal exception to signal a non-enforcing SELinux. *) > + > (* Simple reimplementation of Array.mem, available only with OCaml >= 4.03. *) > let array_find a l > List.mem a (Array.to_list l) > @@ -35,12 +38,18 @@ let rec relabel (g : G.guestfs) > use_setfiles g; > (* That worked, so we don't need to autorelabel. *) > g#rm_f "/.autorelabel" > - with Failure _ -> > + with > + | Failure _ -> > (* This is the fallback in case something in the setfiles > * method didn't work. That includes the case where a non-SELinux > * host is processing an SELinux guest, and other things. > *) > g#touch "/.autorelabel" > + | SELinux_not_enforcing -> > + (* This means that SELinux was not configured to be in enforcing mode, > + * so silently accept this. > + *) > + () > ) > > and is_selinux_guest g > @@ -59,6 +68,21 @@ and use_setfiles g > g#aug_load (); > debug_augeas_errors g; > > + (* Get the SELinux enforcing mode, eg "enforcing", "permissive", > + * "disabled". > + * Use "disabled" if not specified, just like libselinux seems to do. > + *) > + let typ = read_selinux_config_key g "SELINUX" "disabled" in > + (* Do not attempt any relabelling if the SELinux is not "enforcing": > + * - in "permissive" mode SELinux is still running, however nothing is > + * enforced: this means labels can be wrong, and "it is fine"I don't think it's fine. As I showed here: https://www.redhat.com/archives/libguestfs/2020-June/msg00115.html in permissive mode labels are still being updated on disk. TBH I don't understand what you said here: https://www.redhat.com/archives/libguestfs/2020-June/msg00117.html about "both the labels and the policy may be all wrong". If the administrator set the policy to permissive then labels ought still to be updated when the guest is running, and we ought to try to keep them updated if we can in v2v. It's also fine for an administrator to switch a system to permissive and then back to enforcing without relabelling or rebooting.> + * - when "disabled" means SELinux is not running, so any relabelling > + * is pointless (other than potentially fail due to an invalid > + * SELINUXTYPE configuration)Here you're correct. Once the admin disabled SELinux, labels are going to quickly get out of step with reality, and so attempting to relabel in virt-v2v is indeed a waste of time. I'd accept this series if you changed "not enforcing" to "not enforcing or permissive". Rich.> + *) > + if typ <> "enforcing" then > + raise SELinux_not_enforcing; > + > (* Get the SELinux policy name, eg. "targeted", "minimum". > * Use "targeted" if not specified, just like libselinux does. > *) > -- > 2.26.2 > > _______________________________________________ > Libguestfs mailing list > Libguestfs@redhat.com > https://www.redhat.com/mailman/listinfo/libguestfs-- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-p2v converts physical machines to virtual machines. Boot with a live CD or over the network (PXE) and turn machines into KVM guests. http://libguestfs.org/virt-v2v
Pino Toscano
2020-Nov-11 11:52 UTC
Re: [Libguestfs] [common PATCH 0/3] SELinux_relabel: relabel only if enforcing (RHBZ#1828952)
On Wednesday, 23 September 2020 17:57:47 CET Pino Toscano wrote:> Continuation/rework of: > https://www.redhat.com/archives/libguestfs/2020-May/msg00020.html > > This is my approach, as I explained here: > https://bugzilla.redhat.com/show_bug.cgi?id=1828952#c4 > https://www.redhat.com/archives/libguestfs/2020-May/msg00035.html > IOW: do not attempt to relabel if the guest is not enforcing, as it is > either useless or may fail; few words more are in the comments of patch > #3.Are there any non-ideological actual technical objection to this patch series? If not, I'll push it in a week. Thanks, -- Pino Toscano
Richard W.M. Jones
2020-Nov-16 08:21 UTC
Re: [Libguestfs] [common PATCH 0/3] SELinux_relabel: relabel only if enforcing (RHBZ#1828952)
On Wed, Nov 11, 2020 at 12:52:31PM +0100, Pino Toscano wrote:> On Wednesday, 23 September 2020 17:57:47 CET Pino Toscano wrote: > > Continuation/rework of: > > https://www.redhat.com/archives/libguestfs/2020-May/msg00020.html > > > > This is my approach, as I explained here: > > https://bugzilla.redhat.com/show_bug.cgi?id=1828952#c4 > > https://www.redhat.com/archives/libguestfs/2020-May/msg00035.html > > IOW: do not attempt to relabel if the guest is not enforcing, as it is > > either useless or may fail; few words more are in the comments of patch > > #3. > > Are there any non-ideological actual technical objection to this patch > series? > > If not, I'll push it in a week.Yes, I have technical objections. I do not have any "ideological" objections to it. Please do not push the patch as is. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/
Reasonably Related Threads
- Re: [common PATCH 3/3] mlcustomize: do not relabel if not enforcing (RHBZ#1828952)
- Re: [common PATCH 3/3] mlcustomize: do not relabel if not enforcing (RHBZ#1828952)
- [common PATCH 0/3] SELinux_relabel: relabel only if enforcing (RHBZ#1828952)
- [PATCH libguestfs-common 1/2] mlcustomize: Refactor SELinux_relabel code.
- [PATCH libguestfs-common 2/2] mlcustomize: Fall back to autorelabel if specfile does not exist (RHBZ#1828952).